Jump to content

2017 KTM 500 EXC running rich

Recommended Posts

Kugs mystery ride begat another mystery.  So I'm about 100 feet into the ride when the bike stalls. Restart ride another 100, stalls again. Hard to keep it running just above idle or long idle.  Lets go faster and try to blow it out is the suggestion.  Starts fine and so I whip it up and runs great at half throttle and above .  Close the throttle into a corner and blah, wants to die.  Well, better turn around now before it gets worse.  So back to staging place at Socalmules (Thanks Mark!) to scope it out.  From others it smells rich and does seem to be running rich at low end.  Pull the freshly serviced air filter to take a look.  Runs same without filter.  Check the tank breather to find its not breathing.  We leave the breather off the tank and no difference, runs same - just as before. Lots of speculation on our end (fuel pump? faulty JD tuner?) so decided to pack up and call it quits and let the others (2) go about the mystery ride, which was changing by the minute.

So I had a good hour ride home to think about it.  Look at the Tank vent first as that was odd.  Pull the tank and start following vent lines.  Nothing appears pinched up top.  One goes below the engine so I pull the skid plate and as soon as the nuts are loose, a good 3 to 4 ounces of fuel pours out.  I see where the vent was pinched between frame and skid plate (see photo).  My bad.  The whole Evap system was full of fuel.  With the bike running, which has not been fully de-smogged, the emissions solenoid was opening to draw fuel vapor but instead was drawing fuel and causing a rich fuel condition.  The large diameter down tube with plug which acts as a storage vessel was also full of fuel (see photo).

Curious that it did this now as I've ridden with it this way to two ride this season already with a good 150 miles with no problems.  This ride, I tanked up pretty full so there is a thought that the tank was being collapsed by the drawing of fuel from the fuel pump, causing the fuel to be pushed out the tank vent into the Evap canister (yet I only rode it a few 100 feet).  I'll have to plug the tank vent to see if its that dramatic of a vacuum to cause that condition to happen. I've been told it can and has happened to others (690s).  Another possibility was the transit over the mountains from coastal to desert caused pressure differentials that pushed fuel into the canister.  Runs fine now.  Glad it was a simple fix, caused by a simple error.  Could have been fixed on site or in the field, but did not know what we were looking for or what we would find. Lesson learned.  A good reason to fully de-smog the critter.  Not sure how long it would have taken to run all the fuel out of the evap system if I just kept riding. 

While I was looking, I put a voltmeter on the emission solenoid and found the voltage changed with RPM.  Idle voltage was high 11's (11.8v but I don't recall the exact numbers) and high numbers were 12.5v (again varied dependent on RPM).  Point is the voltage to the solenoid varied to change the action of the solenoid.  Which way (open vs.closed) I don't know but assume more open with RPM.   



Share this post

Link to post
Share on other sites

Good write-up Van, pretty sure someone in the future will be able to use this experience to their benefit. 

Share this post

Link to post
Share on other sites

Thanks Van. You have been the Guinea pig for the 500,s LOL . Ground wires ect. Glad it was a easy fix. Then Van come to Julian and picked us up today . He is the Man !


Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now